Unconventional oil and gas reservoirs, such as shale oil and gas, coal gas and tight oil and gas and so on, are widely distributed in China and prospective reserves thereof are huge. As such high-efficiency exploitation of unconventional oil and gas reservoirs is a long-term focus in the petroleum industry. An unconventional oil and gas reservoir exhibits the feature of low pore and low permeability. Thus, the high-efficiency exploitation of an unconventional oil reservoir needs large-scale hydraulic fracturing operations to form a large number of and even net-like cracks, with high diversion ability in the reservoir, so that migration conditions for oil and gas are improved.
Multistage hydraulic fracturing is a fracturing and completion method commonly used in horizontal wells. With this method, a large number of hydraulic cracks could be formed at different positions in one reservoir, so that oil and gas drainage volume of the unconventional oil and gas reservoir is increased and resistance for oil and gas migration is reduced. However, stress interference and communication in multistage hydraulic crack determines success rate of hydraulic fracturing in oilfield and the efficiency of the hydraulic crack, which determines directly subsequent exploitation speed of the reservoir and economic benefit. At present, domestic and foreign research institutes are actively seeking to characterize the mechanical mechanism of the interaction of the cracks, studying the stress interference among the cracks through method of indoor physical simulation, and forming a complex fracture network effectively using this interference.